It is well known that the so-called thermodynamic cycle is a closed cycle loop consisting of a plurality of thermodynamic processes. Three or more thermodynamic engineering machines can be connected serially and in parallel to constitute a closed cycle system in which a working medium circulates in order to realize a predetermined thermodynamic cycle.
Through various combinations, one can constitute various thermodynamic cycles from various thermodynamic processes. Each thermodynamic cycle can, according to the circulating direction of the working medium in the system, be classified as a direct cycle or a reverse cycle. In the the temperature entropy diagram, a reverse cycle is when the working medium circulates in the counterclockwise direction.